In order to extend the lifetime of lithium-ion batteries, an advanced thermal management concept is investigated. In battery modules, different cell temperatures lead to higher efforts in cell balancing and reduce the system's lifetime. Especially when battery systems with phase change material operate outside the phase transition range high temperature gradients can occur that result in different ageing speeds of the cells. The effect of temperature dependent ageing of the battery cells is further investigated. A battery module concept is developed with focus on temperature homogenization by optimization of the module design and material characteristics. The module design combines several approaches including optimized interface pads, thermal storage materials and anisotropic multilayer graphite sheets. Numerical simulations with material and geometrical models are used for the evaluation of the concept with reference models. In addition, a battery cell model is set up, which describes the reversible and irreversible heat generation rate. Using model-order-reduction, the simulations are accelerated by reduction of the calculation time. In order to optimize the material parameters, the simulations are analyzed with design exploration techniques. As a result, the overall temperature differences in the module are minimized and the temperature distribution is homogenized with new developed interface pads. In combination with high thermally conductive synthetic graphite sheets the pads also compensate the insulating behavior of thermal storage material, which is used for temperature peak reduction and to smooth temperature changes
In mobile and stationary battery systems, lifetime expectancy is a key parameter for the calculation of monetary effectiveness. It significantly affects return on investment and therefore is a key parameter for the market breakthrough of the desired battery application. Battery life is influenced by two different factors, namely electrical utilization and environmental conditions. As higher temperatures lead to a faster deterioration of the lithium-ion battery, smart thermal design can not only increase battery lifetime, but also reduce cooling costs and improve overall efficiency. It is therefore essential to establish an effective thermal design through perfoming electrothermal modeling and characterization of the battery cell, battery module and fully assembled battery pack. In this paper, the motivation for electrothermal modeling of lithium-ion battery cells and modules is introduced and design challenges are identified for applications in mobile and stationary bat tery systems. An electrothermal model of batteries with appropriate cell chemistry for mobile and stationary applications is developed with focus on further implementation in thermal simulation of battery modules and packs. The parameterization process of the presented models is shown and a model of battery cells with derived parameters is presented. Finally, the electrothermal model is verified experimentally
This paper presents the hardware and software design of a battery monitoring circuit developed to be used in aviation applications employing lithium-ion batteries in their electrified powertrain. The considered aircraft is a manned sailplane able to take-off and climb by using its electric propulsion system supplied by NCA/Graphite lithium-ion batteries. The battery monitoring electronics was developed with the highest considerations in terms of fail-safe and fail-operational requirements. The electronic design of the battery monitoring circuit integrates the battery busbars and uses new passive balancing components with an innovative busbar cooling solution, thus increasing the reliability and the robustness of the whole battery system. The software also contributes to the high safety level by employing crosscheck and plausibility check mechanisms
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